The present invention relates generally to a fuel supply control arrangement for an engine, and more particularly to an improved fuel supply control arrangement for a split-bank, multicylinder engine.
It has been the practice in conjunction with fuel injection systems for engines to provide a pressure relief system so that the fuel pressure at the injector is maintained stable. This is important to ensure that the injection strategy results in the injection of the appropriate amount of fuel for proper engine operation. Normally, the fuel pressure is regulated by a pressure relief valve that returns excess fuel supplied to the injectors, their associated fuel rail, or both back to some place in the supply circuit. The excess fuel may be returned directly to the fuel tank or to other locations in the fuel supply system upstream of the injector.
In order to have excess fuel for pressure regulation, the amount of fuel supplied to the injectors must be somewhat greater than the total amount of fuel which will be consumed by the engine under all running conditions for which pressure regulation is desired. This supply of excess fuel has certain advantages.
If excess fuel is supplied, then it is possible to use the fuel flow to cool certain components of the engine, particularly the fuel injector. Furthermore, by continuously recycling a portion of the fuel, the fuel vapor separator can do a better job of separating vapors from the fuel to ensure that the fuel supplied to the engine is vapor free. Vapors in the fuel will result in the injection of less fuel than desired if the vapors are not separated before delivery to the injectors.
It is also known that the fuel pump must supply adequate amounts of fuel for all operating conditions, particularly under high speed and high load conditions. Thus, if a constantly operated pump is employed, large excesses of fuel will be pumped under low speed and low load conditions. The pumping of large excesses of fuel has certain disadvantages.
Although circulating excess fuel has the advantage of providing cooling for the fuel, the circulation of to much fuel can heat the fuel such that the desired cooling effect is not achieved. Also, if there are gross differences in the amount of fuel supplied, then the pressure regulator may not be capable of providing the desired regulation at all engine speeds and load ranges.
A principal object of the embodiments of the present invention is to provide an improved fuel supply system for an engine.
A further object of the embodiments of the present invention is to provide an improved fuel supply system for an internal combustion engine that will provide appropriate slight excesses of fuel supply under all running conditions.
The embodiments of the present invention are adapted to be embodied in a fuel supply system for an engine. The fuel supply system includes a tank that stores fuel, a fuel injector that injects the fuel to the engine, and an electrically driven pump that pumps fuel from the tank to the fuel injector through a conduit. A bypass system is provided for returning excess fuel pumped by the fuel pump to the injectors back to a supply side of the system. Means are provided for monitoring engine conditions to detect the amount of fuel being consumed. When the fuel consumption is determined to be lower than a predetermined value, then the electrically driven pump is driven at a lower rate.
One aspect of the present invention is a fuel supply system for an internal combustion engine. The fuel supply system provides fuel to the internal combustion engine. The fuel supply system comprises at least one fuel pump driven by an electric motor, and an electronic control unit that controls the electric motor to control the fuel flow through the fuel pump in response to engine speed, fuel temperature and fuel pressure.
Preferably, the fuel pump is a low pressure pump supplying the fuel to a vapor separator, wherein the speed of the low pressure fuel pump is controlled by the electronic control unit dependent on engine speed, fuel pressure, and fuel temperature. The engine speed is determined using an engine speed sensor, the fuel temperature is determined using a fuel temperature sensor, and the fuel pressure is determined using a fuel pressure sensor. A fuel pressure relief valve relieves fuel pressure from the pressure side of the low pressure fuel pump and delivers the fuel to the scavenge side of the low pressure fuel pump. Preferably, the fuel pressure sensors and the fuel temperature sensor are located on the pressure side of the low pressure fuel pump and before the pressure relief valve circuit.
Within the internal combustion engine, a plurality of fuel injectors are in communication with a high pressure fuel pump being supplied by the vapor separator. The fuel injectors deliver vaporless fuel to at least one intake port or directly into at least one combustion chamber.
The internal combustion engine is advantageously a marine engine. For example, the marine engine provides power to a watercraft. In preferred embodiments, the marine engine is an outboard motor.